Hop plant is a vigorous climbing herbaceous perennial, usually trained to grow up on strings in commercial production. The string is used to provide a connection between the ground and the overhead trellis wires for hop plants. The twining process comprises two primary tasks: to tie an end of the string in a knot on the trellis wire and to stake the other end of the string into the ground. Currently, the knot tying task in hop production fields is performed manually by skilled workers.
Trellis networks are usually 18 feet off the ground and twining is labor intensive. Motivated by shortage in skilled twinning worker supply and increasing labor costs, hop producers have a significant need for practical, reliable automated solutions to twining operation. There have been few developments in hop twining in recent history. For example, Gentry and Giannini, in U.S. Pat. No. 3,563,583, describe a knot-tying machine designed for providing a series of knots in selected spaced locations on a horizontal wire.